Image Details
Caption: Figure 4.
Results of the Swift-XRT monitoring campaign of BL Lac. Fluxes F 0.5−2 keV and F 2−10 keV are displayed in units of 10−12 erg cm−2 s−1 and 10−11 erg cm−2 s−1, respectively. The label “HR” stands for hardness ratio, which we define as (F 2−10 keV − F 0.5−2 keV)/(F 2−10 keV + F 0.5−2 keV). Gray shaded areas mark the duration of the IXPE pointing.
© 2025. The Author(s). Published by the American Astronomical Society.